diff --git a/main/exercise/hotspot_actionscript_admin.as.php b/main/exercise/hotspot_actionscript_admin.as.php
index 4adaadf66f..7eb082ee89 100755
--- a/main/exercise/hotspot_actionscript_admin.as.php
+++ b/main/exercise/hotspot_actionscript_admin.as.php
@@ -1,6 +1,8 @@
 <?php
 /* For licensing terms, see /license.txt */
 
+use ChamiloSession as Session;
+
 /**
 * This file generates the ActionScript variables code used by the HotSpot .swf
 * @package chamilo.exercise
@@ -61,7 +63,7 @@ $i = 0;
 $nmbrTries = 0;
 $answer_type = $objQuestion->type;
 
-$answers = $_SESSION['tmp_answers'];
+$answers = Session::read('tmp_answers');
 $nbrAnswers = count($answers['answer']);
 
 for ($i = 1; $i <= $nbrAnswers; $i++) {
diff --git a/main/exercise/upload_exercise.php b/main/exercise/upload_exercise.php
index d4ecc90ff0..090219e98b 100755
--- a/main/exercise/upload_exercise.php
+++ b/main/exercise/upload_exercise.php
@@ -14,6 +14,7 @@ $help_content = 'exercise_upload';
 require_once __DIR__.'/../inc/global.inc.php';
 
 $is_allowed_to_edit = api_is_allowed_to_edit(null, true);
+$debug = false;
 $origin = api_get_origin();
 if (!$is_allowed_to_edit) {
     api_not_allowed(true);
@@ -538,11 +539,10 @@ function lp_upload_quiz_action_handling()
             }
         }
 
-        if (isset($_SESSION['lpobject'])) {
-            if ($debug > 0) {
-                error_log('New LP - SESSION[lpobject] is defined', 0);
-            }
-            $oLP = unserialize($_SESSION['lpobject']);
+        $lpObject = Session::read('lpobject');
+
+        if (!empty($lpObject)) {
+            $oLP = unserialize($lpObject);
             if (is_object($oLP)) {
                 if ($debug > 0) {
                     error_log('New LP - oLP is object', 0);
@@ -555,7 +555,7 @@ function lp_upload_quiz_action_handling()
                     Session::erase('oLP');
                     Session::erase('lpobject');
                 } else {
-                    $_SESSION['oLP'] = $oLP;
+                    Session::write('oLP', $oLP);
                 }
             }
         }
@@ -564,9 +564,16 @@ function lp_upload_quiz_action_handling()
             $previous = $_SESSION['oLP']->select_previous_item_id();
             $parent = 0;
             // Add a Quiz as Lp Item
-            $_SESSION['oLP']->add_item($parent, $previous, TOOL_QUIZ, $quiz_id, $quizTitle, '');
+            $_SESSION['oLP']->add_item(
+                $parent,
+                $previous,
+                TOOL_QUIZ,
+                $quiz_id,
+                $quizTitle,
+                ''
+            );
             // Redirect to home page for add more content
-            header('location: ../lp/lp_controller.php?'.api_get_cidreq().'&action=add_item&type=step&lp_id='.intval($_GET['lp_id']));
+            header('Location: ../lp/lp_controller.php?'.api_get_cidreq().'&action=add_item&type=step&lp_id='.intval($_GET['lp_id']));
             exit;
         } else {
             //  header('location: exercise.php?' . api_get_cidreq());
diff --git a/main/inc/ajax/lp.ajax.php b/main/inc/ajax/lp.ajax.php
index 50b6303c9a..cc86978f34 100755
--- a/main/inc/ajax/lp.ajax.php
+++ b/main/inc/ajax/lp.ajax.php
@@ -41,9 +41,11 @@ switch ($action) {
         break;
     case 'add_lp_item':
         if (api_is_allowed_to_edit(null, true)) {
-            if ($_SESSION['oLP']) {
+            /** @var learnpath $learningPath */
+            $learningPath = Session::read('oLP');
+            if ($learningPath) {
                 // Updating the lp.modified_on
-                $_SESSION['oLP']->set_modified_on();
+                $learningPath->set_modified_on();
                 $title = $_REQUEST['title'];
                 if ($_REQUEST['type'] == TOOL_QUIZ) {
                     $title = Exercise::format_title_variable($title);
@@ -52,7 +54,7 @@ switch ($action) {
                 $parentId = isset($_REQUEST['parent_id']) ? $_REQUEST['parent_id'] : '';
                 $previousId = isset($_REQUEST['previous_id']) ? $_REQUEST['previous_id'] : '';
 
-                echo $_SESSION['oLP']->add_item(
+                echo $learningPath->add_item(
                     $parentId,
                     $previousId,
                     $_REQUEST['type'],
@@ -187,7 +189,11 @@ switch ($action) {
             break;
         }
 
-        $learningPath = learnpath::getLpFromSession(api_get_course_id(), $lpId, api_get_user_id());
+        $learningPath = learnpath::getLpFromSession(
+            api_get_course_id(),
+            $lpId,
+            api_get_user_id()
+        );
         $lpItem = $learningPath->getItem($lpItemId);
 
         if (empty($lpItem)) {
diff --git a/main/inc/email_editor.php b/main/inc/email_editor.php
index c7fe0b57a2..6cb1dc3567 100755
--- a/main/inc/email_editor.php
+++ b/main/inc/email_editor.php
@@ -14,13 +14,13 @@ use ChamiloSession as Session;
 
 require_once __DIR__.'/../inc/global.inc.php';
 
-if (empty($_user['user_id'])) {
+if (empty(api_get_user_id())) {
     api_not_allowed(true);
 }
 
-if (empty($_SESSION['origin_url'])) {
-    $origin_url = $_SERVER['HTTP_REFERER'];
-    Session::write('origin_url', $origin_url);
+$originUrl = Session::read('origin_url');
+if (empty($originUrl)) {
+    Session::write('origin_url', $_SERVER['HTTP_REFERER']);
 }
 
 $action = isset($_GET['action']) ? $_GET['action'] : null;
@@ -95,9 +95,9 @@ if ($form->validate()) {
             get_lang('Anonymous')
         );
     }
-    $orig = $_SESSION['origin_url'];
+    $orig = Session::read('origin_url');
     Session::erase('origin_url');
-    header('location:'.$orig);
+    header('Location:'.$orig);
     exit;
 }
 Display::display_header(get_lang('SendEmail'));
diff --git a/main/inc/lib/document.lib.php b/main/inc/lib/document.lib.php
index 96c91b6c7c..2b2f82800c 100755
--- a/main/inc/lib/document.lib.php
+++ b/main/inc/lib/document.lib.php
@@ -4802,8 +4802,8 @@ class DocumentManager
             copy($from_sys, $to_sys);
         }
 
-        //get  file from tmp directory
-        $_SESSION['temp_audio_nanogong'] = $to_sys;
+        // get file from tmp directory
+        Session::write('temp_audio_nanogong', $to_sys);
 
         return api_get_path(WEB_ARCHIVE_PATH).'temp/audio/'.$file_crip;
     }
@@ -4813,12 +4813,10 @@ class DocumentManager
      */
     public static function removeGeneratedAudioTempFile()
     {
-        if (isset($_SESSION['temp_audio_nanogong'])
-            && !empty($_SESSION['temp_audio_nanogong'])
-            && is_file($_SESSION['temp_audio_nanogong'])) {
-
-            unlink($_SESSION['temp_audio_nanogong']);
-            unset($_SESSION['temp_audio_nanogong']);
+        $tempAudio = Session::read('temp_audio_nanogong');
+        if (!empty(isset($tempAudio)) && is_file($tempAudio)) {
+            unlink($tempAudio);
+            Session::erase('temp_audio_nanogong');
         }
     }
 
diff --git a/main/inc/lib/myspace.lib.php b/main/inc/lib/myspace.lib.php
index 5a5935d22d..c590dd24b7 100644
--- a/main/inc/lib/myspace.lib.php
+++ b/main/inc/lib/myspace.lib.php
@@ -1,6 +1,7 @@
 <?php
 /* For licensing terms, see /license.txt */
 
+use ChamiloSession as Session;
 use CpChart\Cache as pCache;
 use CpChart\Data as pData;
 use CpChart\Image as pImage;
@@ -583,17 +584,19 @@ class MySpace
 
     public static function sort_users($a, $b)
     {
+        $tracking = Session::read('tracking_column');
         return api_strcmp(
-            trim(api_strtolower($a[$_SESSION['tracking_column']])),
-            trim(api_strtolower($b[$_SESSION['tracking_column']]))
+            trim(api_strtolower($a[$tracking])),
+            trim(api_strtolower($b[$tracking]))
         );
     }
 
     public static function rsort_users($a, $b)
     {
+        $tracking = Session::read('tracking_column');
         return api_strcmp(
-            trim(api_strtolower($b[$_SESSION['tracking_column']])),
-            trim(api_strtolower($a[$_SESSION['tracking_column']]))
+            trim(api_strtolower($b[$tracking])),
+            trim(api_strtolower($a[$tracking]))
         );
     }
 
diff --git a/main/inc/lib/notebook.lib.php b/main/inc/lib/notebook.lib.php
index 85df5ad165..8199cd958f 100755
--- a/main/inc/lib/notebook.lib.php
+++ b/main/inc/lib/notebook.lib.php
@@ -1,6 +1,8 @@
 <?php
 /* For licensing terms, see /license.txt */
 
+use ChamiloSession as Session;
+
 /**
  * This class provides methods for the notebook management.
  * Include/require it in your code to use its features.
@@ -258,25 +260,25 @@ class NotebookManager
             Display::return_icon('notes_order_by_title.png', get_lang('OrderByTitle'), '', '32').'</a>';
         echo '</div>';
 
-        if (!isset($_SESSION['notebook_view']) ||
-            !in_array($_SESSION['notebook_view'], array('creation_date', 'update_date', 'title'))
-        ) {
-            $_SESSION['notebook_view'] = 'creation_date';
+        $notebookView = Session::read('notebook_view');
+
+        if (!in_array($notebookView, array('creation_date', 'update_date', 'title'))) {
+            Session::write('notebook_view', 'creation_date');
         }
 
         // Database table definition
         $t_notebook = Database::get_course_table(TABLE_NOTEBOOK);
-        if ($_SESSION['notebook_view'] == 'creation_date' || $_SESSION['notebook_view'] == 'update_date') {
-            $order_by = " ORDER BY ".$_SESSION['notebook_view']." $sort_direction ";
+        if ($notebookView == 'creation_date' || $notebookView == 'update_date') {
+            $order_by = " ORDER BY ".$notebookView." $sort_direction ";
         } else {
-            $order_by = " ORDER BY ".$_SESSION['notebook_view']." $sort_direction ";
+            $order_by = " ORDER BY ".$notebookView." $sort_direction ";
         }
 
         //condition for the session
         $session_id = api_get_session_id();
         $condition_session = api_get_session_condition($session_id);
 
-        $cond_extra = ($_SESSION['notebook_view'] == 'update_date') ? " AND update_date <> ''" : " ";
+        $cond_extra = $notebookView == 'update_date' ? " AND update_date <> ''" : " ";
         $course_id = api_get_course_int_id();
 
         $sql = "SELECT * FROM $t_notebook
diff --git a/main/inc/lib/tracking.lib.php b/main/inc/lib/tracking.lib.php
index cdb014fe67..b198d9a1b3 100755
--- a/main/inc/lib/tracking.lib.php
+++ b/main/inc/lib/tracking.lib.php
@@ -1,6 +1,7 @@
 <?php
 /* For licensing terms, see /license.txt */
 
+use ChamiloSession;
 use Chamilo\CoreBundle\Entity\ExtraField as EntityExtraField;
 use CpChart\Cache as pCache;
 use CpChart\Data as pData;
@@ -85,11 +86,33 @@ class Tracking
                 $messages = 0;
 
                 foreach ($users as $user_data) {
-                    $time += self::get_time_spent_on_the_course($user_data['user_id'], $course_info['code'], $sessionId);
-                    $avg_student_score += self::get_avg_student_score($user_data['user_id'], $course_info['code'], array(), $sessionId);
-                    $avg_student_progress += self::get_avg_student_progress($user_data['user_id'], $course_info['code'], array(), $sessionId);
-                    $work += self::count_student_assignments($user_data['user_id'], $course_info['code'], $sessionId);
-                    $messages += self::count_student_messages($user_data['user_id'], $course_info['code'], $sessionId);
+                    $time += self::get_time_spent_on_the_course(
+                        $user_data['user_id'],
+                        $course_info['code'],
+                        $sessionId
+                    );
+                    $avg_student_score += self::get_avg_student_score(
+                        $user_data['user_id'],
+                        $course_info['code'],
+                        array(),
+                        $sessionId
+                    );
+                    $avg_student_progress += self::get_avg_student_progress(
+                        $user_data['user_id'],
+                        $course_info['code'],
+                        array(),
+                        $sessionId
+                    );
+                    $work += self::count_student_assignments(
+                        $user_data['user_id'],
+                        $course_info['code'],
+                        $sessionId
+                    );
+                    $messages += self::count_student_messages(
+                        $user_data['user_id'],
+                        $course_info['code'],
+                        $sessionId
+                    );
                 }
 
                 $countUsers = count($users);
@@ -7052,17 +7075,19 @@ class TrackingCourseLog
 
     public function sort_users($a, $b)
     {
+        $tracking = ChamiloSession::read('tracking_column');
         return strcmp(
-            trim(api_strtolower($a[$_SESSION['tracking_column']])),
-            trim(api_strtolower($b[$_SESSION['tracking_column']]))
+            trim(api_strtolower($a[$tracking])),
+            trim(api_strtolower($b[$tracking]))
         );
     }
 
     public function sort_users_desc($a, $b)
     {
+        $tracking = ChamiloSession::read('tracking_column');
         return strcmp(
-            trim(api_strtolower($b[$_SESSION['tracking_column']])),
-            trim(api_strtolower($a[$_SESSION['tracking_column']]))
+            trim(api_strtolower($b[$tracking])),
+            trim(api_strtolower($a[$tracking]))
         );
     }
 
diff --git a/main/lp/aicc_api.php b/main/lp/aicc_api.php
index 1a4da29031..52423e55b5 100755
--- a/main/lp/aicc_api.php
+++ b/main/lp/aicc_api.php
@@ -32,7 +32,7 @@ $use_anonymous = true;
 require_once __DIR__.'/../inc/global.inc.php';
 
 // Is this needed? This is probabaly done in the header file.
-$file = $_SESSION['file'];
+$file = Session::read('file');
 $oLP = unserialize(Session::read('lpobject'));
 $oItem = $oLP->items[$oLP->current];
 if (!is_object($oItem)) {
diff --git a/main/lp/download.php b/main/lp/download.php
index 46ae6fa8e2..7b7e11192d 100755
--- a/main/lp/download.php
+++ b/main/lp/download.php
@@ -35,7 +35,6 @@ if ($_SESSION['oLP']) {
     $lp_item_id = $_SESSION['oLP']->current;
     $lp_item_info = new learnpathItem($lp_item_id);
     if (!empty($lp_item_info)) {
-        //if (basename($lp_item_info->path) == basename($doc_url)) {
         $visible = learnpath::is_lp_visible_for_student($lp_id, $user_id);
 
         if ($visible) {